U.S. patent application number 10/097018 was filed with the patent office on 2002-10-24 for stirling engine.
Invention is credited to Asai, Masahiro, Ban, Masaki.
Application Number | 20020152750 10/097018 |
Document ID | / |
Family ID | 26611218 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020152750 |
Kind Code |
A1 |
Asai, Masahiro ; et
al. |
October 24, 2002 |
Stirling engine
Abstract
To provide a Stirling engine and a control unit for a Stirling
engine capable of disposing a displacer unit and a power cylinder
unit separately from each other, thereby increasing the degree of
freedom of layout thereof. A displacer unit and a power cylinder
unit of a Stirling engine E are disposed separately from each
other. A compression chamber of the displacer unit is connected to
an operation chamber of the power cylinder unit via a pressure
conduit. A control actuator capable of arbitrarily controlling the
displacer piston of the displacer unit is connected to the
displacer piston.
Inventors: |
Asai, Masahiro; (Saitama,
JP) ; Ban, Masaki; (Saitama, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
26611218 |
Appl. No.: |
10/097018 |
Filed: |
March 14, 2002 |
Current U.S.
Class: |
60/520 ;
623/27 |
Current CPC
Class: |
F02G 2243/30 20130101;
A61F 2002/701 20130101; F02G 2280/005 20130101; A61F 2002/762
20130101; A61F 2002/6614 20130101; F02G 1/043 20130101; A61F 2/70
20130101; A61F 2/64 20130101; A61F 2002/7625 20130101; A61F 2/60
20130101; A61F 2002/704 20130101; A61F 2002/7655 20130101; A61F
2/74 20210801; F02G 2244/50 20130101 |
Class at
Publication: |
60/520 ;
623/27 |
International
Class: |
F25B 009/00; F02G
001/04; F01B 029/10; A61F 002/74 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2001 |
JP |
2001-071796 |
Mar 16, 2001 |
JP |
2001-075568 |
Claims
What is claimed is:
1. A Stirling engine including a displacer unit in which a
displacer piston is slidably fitted in a displacer cylinder for
partitioning an interior portion of said cylinder into an expansion
chamber and a compression chamber, and a power cylinder unit having
a power piston slidably fitted in a power cylinder for forming an
operation chamber in communication with said compression chamber in
said cylinder comprising: said displacer unit and said power
cylinder unit are disposed separately from each other; said
compression chamber is connected to said operation chamber via a
pressure conduit; and a control actuator is operatively connected
to said displacer piston for arbitrarily controlling the movement
of said displacer piston.
2. The Stirling engine according to claim 1, wherein said pressure
conduit has flexibility.
3. The Stirling engine according to claim 1, wherein a hydraulic
converter is operatively connected to said compression chamber for
converting a pressure in said compression chamber to a hydraulic
pressure and transmitting the hydraulic pressure to said operation
chamber, said hydraulic converter being provided between said
compression chamber and said pressure conduit.
4. The Stirling engine according to claim 2, wherein a hydraulic
converter is operatively connected to said compression chamber for
converting a pressure in said compression chamber to a hydraulic
pressure and transmitting the hydraulic pressure to said operation
chamber, said hydraulic converter being provided between said
compression chamber and said pressure conduit.
5. The Stirling engine according to claim 2, wherein said control
actuator determines a walking movement and thereafter controls the
displacer piston for imparting a walking movement operation to said
operation chamber.
6. The Stirling engine according to claim 2, wherein said control
actuator determines a running movement and thereafter controls the
displacer piston for imparting a running movement operation to said
operation chamber.
7. The Stirling engine according to claim 2, wherein said control
actuator determines a slope ascending movement and thereafter
controls the displacer piston for imparting a slope ascending
movement operation to said operation chamber.
8. The Stirling engine according to claim 2, wherein said control
actuator determines a slope descending movement and thereafter
controls the displacer piston for imparting a slope descending
movement operation to said operation chamber.
9. The Stirling engine according to claim 2, wherein said control
actuator determines a stairs ascending movement and thereafter
controls the displacer piston for imparting a stairs ascending
movement operation to said operation chamber.
10. The Stirling engine according to claim 2, wherein said control
actuator determines a stairs descending movement and thereafter
controls the displacer piston for imparting a stairs descending
movement operation to said operation chamber.
11. A control system for a Stirling engine including a displacer
unit in which a displacer piston is slidably fitted in a displacer
cylinder for partitioning an interior portion of said cylinder into
an expansion chamber and a compression chamber, and a power
cylinder unit having a power piston slidably fitted in a power
cylinder for forming an operation chamber in communication with
said compression chamber in said cylinder said control system
comprising: displacer piston driving means for driving said
displacer piston; displacer piston position detecting means for
detecting a position of said displacer piston; power piston
position detecting means for detecting a position of said power
piston; and a control unit for controlling an operation of said
displacer driving means on the basis of detection signals from both
said displacer piston position detecting means and said power
piston position detecting means.
12. The control system for a Stirling engine according to claim 11,
wherein said displacer piston driving means is operated by said
control unit for changing a difference in phase between said
displacer piston and said power piston.
13. A control system for a Stirling engine including a displacer
unit in which a displacer piston is slidably fitted in a displacer
cylinder for partitioning an interior portion of said cylinder into
an expansion chamber and a compression chamber, and a power
cylinder unit having a power piston slidably fitted in a power
cylinder for forming an operation chamber in communication with
said compression chamber in said cylinder, said control system
comprising: displacer piston driving means for driving said
displacer piston; heat control means for controlling heat generated
by a heating portion of said displacer cylinder; displacer piston
position detecting means for detecting a position of said displacer
piston; power piston position detecting means for detecting a
position of said power piston; and a control unit for controlling
an operation of said heat control means on the basis of detection
signals from both said displacer piston position detecting means
and said power piston position detecting means.
14. A control system for a Stirling engine including a displacer
unit in which a displacer piston is slidably fitted in a displacer
cylinder for partitioning an interior portion of said cylinder into
an expansion chamber and a compression chamber and a power cylinder
unit having a power piston slidably fitted in a power cylinder for
forming an operation chamber in communication with said compression
chamber in said cylinder, said control system comprising: displacer
piston driving means for driving said displacer piston; load
adjusting means for adjusting a load of a load apparatus connected
to said power piston; displacer piston position detecting means for
detecting a position of said displacer piston; power piston
position detecting means for detecting a position of said power
piston; and a control unit for controlling an operation of said
load adjusting means on the basis of detection signals from both
said displacer piston position detecting means and said power
piston position detecting means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 USC 119 to
Japanese Patent Application Nos. 2001-071796 filed on Mar. 14, 2001
and 2001-075568 filed on Mar. 16, 2001 the entire contents thereof
are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a Stirling engine and a
control system for a Stirling engine including a displacer unit in
which a displacer piston is slidably fitted in a displacer cylinder
so as to partition the inside of the cylinder into an expansion
chamber and a compression chamber. A power cylinder unit is
provided in which a power piston is slidably fitted in a power
cylinder so as to form an operation chamber in communication with
the compression chamber in the cylinder.
DESCRIPTION OF THE BACKGROUND ART
[0003] A Stirling engine is known as disclosed, for example, in a
handbook entitled "Car Engineering Series, Vol. 8 `Electric Car,
New Type Motor`" issued by SANKAIDO Publishing Co., Ltd.
[0004] The above-described Stirling engine has a problem that since
a displacer cylinder and a power cylinder of the Stirling engine
are integrated with each other, the engine is voluminous as a
whole, with a result that in some applications, the degree of
freedom in layout of the engine is reduced.
SUMMARY AND OBJECTS OF THE INVENTION
[0005] In view of the foregoing, the present invention has been
made, and an object of the present invention is to provide a
Stirling engine capable of disposing a displacer unit and a power
cylinder unit separately from each other, and increasing the degree
of freedom of layout of the engine, thereby enhancing the
applicability of the engine.
[0006] In the above-described prior art Stirling engine, since a
displacer piston and a power piston are mechanically connected to
each other with a specific phase difference maintained
therebetween, the phase of the power piston is uniquely determined
by the phase of the displacer piston. Accordingly, since the motion
control of the power piston of the prior art Stirling engine is
performed only by adjusting heat generated by a heating portion of
a displacer unit, the responsiveness of the motion control is
significantly low, and therefore, the application of the prior art
Stirling engine is limited to a power source of an apparatus in
which a variation in load is relatively small.
[0007] In view of the foregoing, the present invention has been
made, and an object of the present invention is to provide a
control unit for a Stirling engine, which is capable of positively
controlling the motion of a power piston with a high responsiveness
and hence to improve the applicability of the Stirling engine.
[0008] To achieve the above object, according to a first feature of
the present invention, there is provided a Stirling engine
including a displacer unit in which a displacer piston is slidably
fitted in a displacer cylinder so as to partition the inside of the
cylinder into an expansion chamber and a compression chamber. A
power cylinder unit is provided in which a power piston is slidably
fitted in a power cylinder so as to form an operation chamber in
communication with the compression chamber in the cylinder. The
displacer unit and the power cylinder unit are disposed separately
from each other. The compression chamber is connected to the
operation chamber via a pressure conduit. A control actuator is
capable of arbitrarily controlling the displacer piston and is
connected to the displacer piston.
[0009] With the first feature, the displacer unit and the power
cylinder unit can be disposed separately from each other, more
specifically, freely disposed at desired positions. As a result, it
is possible to increase the degree of freedom in layout of the
Stirling engine and thereby to enhance the applicability of the
Stirling engine. Further, the power piston of the power cylinder
unit can be freely remote-controlled by controlling a phase and an
operating speed of the displacer piston by means of the control
actuator.
[0010] According to a second feature of the present invention, in
addition to the first feature, the pressure conduit has
flexibility. With this second feature, the displacer unit and the
power cylinder unit can be displaced relative to each other by the
flexibility of the pressure conduit, so that the displacer unit and
the power cylinder unit can be disposed without interference
therebetween. As a result, it is possible to further increase the
degree of freedom in layout of the Stirling engine and hence to
further enhance the applicability of the Stirling engine.
[0011] According to a third feature of the present invention, in
addition to the first or second feature, a hydraulic converter for
converting a pressure in the compression chamber to a hydraulic
pressure and transmitting the hydraulic pressure to the operation
chamber is provided between the compression chamber and the
pressure conduit.
[0012] With this third feature, since a pressure in the compression
chamber of the displacer unit is converted into a hydraulic
pressure by the hydraulic converter and the hydraulic pressure is
transmitted to the operation chamber, elastic compression, which is
liable to occur in the case of using a working gas as a
transmission medium, does not occur in both the pressure conduit
and the operation chamber, so that it is possible to improve a
pressure transmission efficiency. Further, since the pressure
conduit is filled with a non-compressive fluid, it is possible to
eliminate a possibility that an inner volume of the pressure
conduit becomes a dead volume of the Stirling engine, and hence to
improve a theoretical efficiency of the Stirling engine.
[0013] According to a fourth feature, there is provided a control
system for a Stirling engine including a displacer unit in which a
displacer piston is slidably fitted in a displacer cylinder so as
to partition the inside of the cylinder into an expansion chamber
and a compression chamber. A power cylinder unit is provided in
which a power piston is slidably fitted in a power cylinder so as
to form an operation chamber in communication with the compression
chamber in the cylinder. The control system includes a displacer
piston driving means for driving the displacer piston, a displacer
piston position detecting means for detecting a position of the
displacer piston, a power piston position detecting means for
detecting a position of the power piston and a control unit for
controlling an operation of the displacer driving means on the
basis of detection signals from both piston position detecting
means.
[0014] With this fourth feature, it is possible to control the
motion of the power piston with a high responsiveness by operating
the displacer piston at a suitable time by the displacer driving
means, and hence to increase the applicability of the Stirling
engine. In particular, since the operation of the displacer driving
means is controlled by the control unit on the basis of a detection
of signals from the displacer piston position detecting means and
the power piston position detecting means, it is possible to freely
control the operation, stoppage, an operating speed and a stopped
position of the power piston irrespective of heat generated by the
heating portion of the displacer unit.
[0015] According to a fifth feature of the present invention, the
displacer piston driving means is operated by the control unit so
as to change a difference in phase between the displacer piston and
the power piston.
[0016] With this fifth feature, it is possible to freely control an
operating timing and a stopping timing of the power piston.
[0017] According to a sixth feature of the present invention, there
is provided a control system for a Stirling engine including a
displacer unit in which a displacer piston is slidably fitted in a
displacer cylinder so as to partition the inside of the cylinder
into an expansion chamber and a compression chamber. A power
cylinder unit is provided in which a power piston is slidably
fitted in a power cylinder so as to form an operation chamber in
communication with the compression chamber in the cylinder. The
control system includes a displacer piston driving means for
driving the displacer piston, a heat control means for controlling
a heat generated by a heating portion of the displacer cylinder, a
displacer piston position detecting means for detecting a position
of the displacer piston, a power piston position detecting means
for detecting a position of the power piston and a control unit for
controlling an operation of the heat control means on the basis of
detection signals from both piston position detecting means.
[0018] With this sixth feature, it is possible to control the
motion of the power piston with a high responsiveness by operating
the displacer piston at a suitable time by the displacer driving
means, and hence to increase the applicability of the Stirling
engine. In particular, since the operation of the heat control
means for controlling heat generated by the heating portion of the
displacer cylinder is controlled by the control unit on the basis
of detection signals from the displacer piston position detecting
means and the power piston position detecting means, it is possible
to efficiently use heat generated by the heating portion.
[0019] According to a seventh feature of the present invention,
there is provided a control system for a Stirling engine including
a displacer unit in which a displacer piston is slidably fitted in
a displacer cylinder so as to partition the inside of the cylinder
into an expansion chamber and a compression chamber, and a power
cylinder unit in which a power piston is slidably fitted in a power
cylinder so as to form an operation chamber in communication with
the compression chamber in the cylinder. The control system
includes a displacer piston driving means for driving the displacer
piston, a load adjusting means for adjusting a load of a load
apparatus connected to the power piston, a displacer piston
position detecting means for detecting a position of the displacer
piston, a power piston position detecting means for detecting a
position of the power piston and a control unit for controlling an
operation of the load adjusting means on the basis of detection
signals from both piston position detecting means.
[0020] With this seventh feature, it is possible to control the
motion of the power piston with a high responsiveness by operating
the displacer piston at a suitable time by the displacer driving
means, and hence to increase the applicability of the Stirling
engine. In particular, since the operation of the load adjusting
means is controlled by the control unit on the basis of detection
signals from the displacer piston position detecting means and the
power piston position detecting means, it is possible to stabilize
the output from the power piston even if the heat generated by the
heating portion is somewhat varied.
[0021] The displacer driving means is equivalent to each of
actuators 20, 20A and 20B to be described in embodiments of the
present invention. The displacer piston position detecting means is
equivalent to a displacer piston sensor 21. The power piston
position detecting means is equivalent to a bending/stretching
sensor 51 or a power piston sensor. The heat control means is
equivalent to a fuel adjuster 44.
[0022] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0024] FIG. 1 is a rear view of a user wearing a drive unit for a
prosthetic limb including a Stirling engine according to a first
embodiment of the present invention;
[0025] FIG. 2 is a vertical sectional view of the Stirling
engine;
[0026] FIG. 3 is a vertical sectional view showing an example of an
actuator for the Stirling engine;
[0027] FIG. 4 is a perspective view showing another example of the
actuator;
[0028] FIG. 5 is a perspective view of a further example of the
actuator;
[0029] FIG. 6 is a flow diagram showing a control system of the
Stirling engine;
[0030] FIG. 7 is a schematic view showing a second embodiment of
the present invention, corresponding to FIG. 1;
[0031] FIG. 8 is a front view of a wheelchair according to a third
embodiment of the present invention;
[0032] FIG. 9 is a vertical sectional view of a Stirling engine
according to a fourth embodiment of the present invention;
[0033] FIG. 10 is a vertical sectional view of a Stirling engine
according to a fifth embodiment of the present invention;
[0034] FIG. 11 is a vertical sectional view of a Stirling engine
according to a sixth embodiment of the present invention; and
[0035] FIGS. 12(a), 12(b) and 12(c) are vertical sectional views
showing configurations of a Stirling engine according to a seventh
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings.
[0037] A first embodiment of the present invention shown in FIGS. 1
and 2 will be described below. In FIGS. 1 and 2, a Stirling engine
E of the present invention is illustrated which is typically used
for driving a prosthetic leg 1. The prosthetic leg 1 includes a
thigh portion 2 integrated with a socket 2a in which a user's
remaining thigh portion is to be inserted. A shank portion 4 is
bendably/stretchably connected to a lower end of the thigh portion
2 via a joint 3. A foot portion 5 is connected to a lower end of
the shank portion 4.
[0038] The Stirling engine E includes a displacer unit 6 and a
control unit 7, which are mounted on a belt B worn around a user's
waist portion. A power cylinder unit 8 is mounted on the prosthetic
leg 1 at a position between the thigh portion 2 and the shank
portion 4. A pressure conduit 22 is provided for transmitting a
pressure generated in the displacer unit 6 to the power cylinder
unit 8. A configuration of such a Stirling engine E will be more
fully described with reference to FIG. 2.
[0039] The displacer unit 6 includes a displacer cylinder 10. A
displacer piston 13 is slidably inserted in the cylinder 10 so as
to partition the inside of the cylinder 10 into an expansion
chamber 11 on a head side of the cylinder 10 and a compression
chamber 12 on a bottom side of the cylinder 10. A combustor 14,
provided around the head portion of the displacer cylinder 10, is
provided for heating the expansion chamber 11. A radiator 15 is
provided on the bottom portion of the displacer cylinder 10 for
cooling the compression chamber 12. A heat regenerator 17 is
interposed in a communication port 16 for connecting the expansion
chamber 11 to the compression chamber 12. A motor-driven control
actuator 20 is provided for driving the displacer piston 13 via a
rod 13a passing through the bottom portion of the displacer
cylinder 10. A displacer piston sensor 21 for detecting a position
of the displacer piston 13 is provided on the control actuator
20.
[0040] The combustor 14 is of a catalyst type in which a combustion
housing 25, formed on an outer surface of the head portion of the
displacer cylinder 10, is filled with catalyst 26 for combustion. A
fuel-air mixer 27 is provided at one end portion of the combustion
housing 25 and an exhaust pipe 28 is provided at the other end of
the housing 25.
[0041] A heat exchange wall 29 for covering the combustion housing
25 and a base portion of the exhaust pipe 28 is formed around the
combustion housing 25. A shroud 30 for covering the heat exchange
wall 29 is formed around the heat exchange wall 29. An air intake
port 31, formed in the shroud 30, is in communication with an air
inlet of the fuel-air mixer 27 via an air passage 32 meandering in
each space between two of the combustion housing 25, the heat
exchange wall 29, and the shroud 30.
[0042] A thermal-electric converting device 34 is additionally
provided on the shroud 30 at a position near the heat exchange wall
29. The thermal-electric converting device 34 converts heat
transferred from the heat exchange wall 29 into electricity, to
charge a storage battery 39 with electricity. A supporting wall 35
for containing the control actuator 20 while supporting a fixed
portion of the actuator 20 is provided in such a manner so as to be
continuous to the shroud 30.
[0043] The control unit 7 includes an electronic control unit 37, a
fuel cartridge 38, the storage battery 39 as a power source for the
electronic control unit 37, and a manually operated controller 40
for arbitrarily operating the electronic control unit 37. The
electronic control unit 37, the fuel cartridge 38, and the storage
battery 39 are contained in a control box 41. The fuel cartridge 38
is filled with a fuel such as benzine, alcohol, or LPG
[0044] A fuel outlet of the fuel cartridge 38 is connected to a
fuel inlet of the fuel-air mixer 27 via a fuel conduit 42. A fuel
adjuster 44 for adjusting a flow rate of fuel is interposed in the
fuel conduit 42. An ignition plug 45 is provided in the combustion
housing 25 at a position adjacent to the mixer 27.
[0045] The power cylinder unit 8 includes a power cylinder 47
pivotably connected to one of the thigh portion 2 and the shank
portion 4, and a power piston 48 pivotably connected to the other
of the thigh portion 2 and the shank portion 4 while slidably
inserted in the power cylinder 47. An operation chamber 49 defined
in the power cylinder 47 by means of the power piston 48 is
communicated to the compression chamber 12 of the displacer unit 6
via the pressure conduit 22.
[0046] A bending/stretching sensor 51 (that is, a power piston
sensor) for detecting a bending/stretching angle between both the
thigh portion 2 and the shank portion 4 is mounted therebetween. An
output signal from the bending/stretching sensor 51 and output
signals from the manually operated controller 40 and the displacer
piston sensor 21 are inputted into the electronic control unit 37.
On the basis of these signals, the electronic control unit 37
controls the actuator 20 and the fuel adjuster 44.
[0047] Examples of the actuators 20 will be described with
reference to FIGS. 3 to 5.
[0048] The actuator 20 shown in FIG. 3 is configured as a voice
coil motor. A magnet 61 is fixed on an inner end wall of a
cylindrical yoke 60 with its bottom closed. A cylindrical movable
coil 63, which is movable in the axial direction, is provided so as
to surround a magnetic pole piece 62 connected to a leading end of
the magnet 61. A rod 13a connected to the displacer piston 13 is
connected to the cylindrical movable coil 63. An annular lead wire
holder 64 is connected to an open end of the yoke 60, and a
diaphragm 65 is stretched between the lead wire holder 64 and the
rod 13a. A stroke sensor for detecting a position of the movable
coil 63, which functions as a displacer piston sensor 21, is
provided on an end wall of the yoke 60.
[0049] With this configuration, by repeatedly switching a direction
along which current is applied to the movable coil 63, the
displacer piston 13 can be reciprocated via the rod 13a by an
interaction between a magnetic force generated from the movable
coil 63 and a magnetic force of the magnet 61.
[0050] The actuator 20 shown in FIG. 4 is configured by connecting
the rod 13a to a rotor 67r of a normally/reversely rotatable
electric motor 67 via a ball screw 68. In this case, the rotation
of the rod 13a is prohibited by rotation-stop means (not shown). An
encoder for detecting an angular position of rotation of the rotor
67r, which functions as the displacer piston sensor 21, is provided
on a stator 67s of the electric motor 67.
[0051] With this configuration, the displacer piston 13 can be
reciprocated via the rod 13a by repeating normal rotation and
reverse rotation of the rotor 67r of the electric motor 67.
[0052] The actuator 20 shown in FIG. 5 is configured such that the
rod 13a is connected to a rotor shaft 70r of a normally/reversely
rotatable electric motor 70 via a rack/pinion mechanism 71. Even in
this case, an encoder for detecting an angular position of rotation
of the rotor shaft 70r, which functions as the displacer piston
sensor 21, is provided on a stator 70s of the electric motor
70.
[0053] With this configuration, the displacer piston 13 can be
reciprocated via the rod 13a by repeating normal rotation and
reverse rotation of the rotor shaft 70r of the electric motor
70.
[0054] The function of the first embodiment will be described
below.
[0055] Fuel is fed from the fuel cartridge 38. The flow rate of the
fuel is adjusted by the fuel adjuster 44. The fuel is then supplied
to the fuel-air mixer 27, to be mixed with air which has flown from
the air intake port 31 into the fuel-air mixer 27 via the air
passage 32. The air-fuel mixture is ignited once by the ignition
plug 45, and thereafter, the combustion of the air-fuel mix is
continuously accelerated by the catalyst 26, to heat the expansion
chamber 11 from the head portion side of the displacer cylinder 10
at a specific high temperature. An exhaust gas generated by the
combustion is discharged to the outside through the exhaust pipe
28.
[0056] The radiator 15 keeps the compression chamber 12 in a
specific low temperature state. The heat regenerator 17 receives
heat from a working gas which is moving between the expansion
chamber 11 and the compression chamber 12 via the communication
port 16.
[0057] The control actuator 20 is operated on the basis of a
command from the electronic control unit 37, to reciprocate the
displacer piston 13, thereby generating a pressure amplitude in the
compression chamber 12. The pressure is transmitted to the
operation chamber 49 of the power cylinder 47 via the flexible
pressure conduit 22, to reciprocate the power piston 48, thereby
bending/stretching the shank portion 4 relative to the thigh
portion 2. The bending/stretching motion of the shank portion 2
relative to the thigh portion 4 assists the walking of the
user.
[0058] At this time, to efficiently drive the power piston 48, the
electronic control unit 37 identifies a position of the power
piston 48 on the basis of an output signal from the
bending/stretching sensor 51, and operates the control actuator 20
such that the displacer piston 13 is in advance of the power piston
48 by a converted crank angle of 90.degree.. Further, the
electronic control unit 37 can control the operational speed of the
displacer piston 13 from zero to an arbitrary value so as to
control the bending/stretching speed of the shank portion 4
relative to the thigh portion 2 from zero to an arbitrary value.
With this configuration, the prosthetic leg 1 can be moved on the
basis of the user's intention.
[0059] Since the combustion form in the catalyst type combustor 14
is continuous combustion, it is possible to enhance a combustion
efficiency and to eliminate any combustion oscillation. In
addition, since the fuel cartridge 38 is adopted, it is possible to
rapidly supplement fuel and also to operate the drive unit for
assisting the walking of the user for a long time.
[0060] Since power consumption of the storage battery 39 as the
power source for the electronic control unit 37 is very small and a
further part of heat generated by the combustor 14 is converted
into an electric energy by the thermal-electric converting device
34 to be stored in the storage battery 39, the useful life of the
storage battery becomes longer.
[0061] Since only the power cylinder unit 8 is provided on the
prosthetic leg 1 while the relatively heavy displacer unit 6, the
fuel cartridge 38, the electronic control unit 37, etc. are mounted
on the belt B worn around the user's waist portion, and the
displacer unit 6 is connected to the power cylinder unit 8 via the
flexible pressure conduit 22, it is possible to make the prosthetic
leg 1 lightweight and slim while ensuring the smooth
bending/stretching motion of the prosthetic leg 1. The prosthetic
leg 1 also allows the user to easily, rapidly, and simply
mount/dismount the displacer unit 6 by mounting/dismounting the
belt B around the waist portion of the user.
[0062] As described above, the displacer unit 6 and the power
cylinder unit 8 can be disposed separately from each other. More
specifically, they can be freely disposed at desired positions. As
a result, it is possible to increase the degree of freedom in
layout of the Stirling engine and enhance the applicability of the
Stirling engine. For example, it is possible to apply the Stirling
engine to drive means for driving an object other than the
prosthetic leg 1. Also, the power piston 48 can freely be
remote-controlled by controlling a phase and an operating speed of
the displacer piston 13 by the control actuator 20.
[0063] The control of the prosthetic leg 1 will be more fully
described with reference to FIG. 6. When receiving a detection
signal from the bending/stretching sensor 51, the electronic
control unit 37 decides a leg action pattern such as a walking,
running, slope ascending, slope descending, stair ascending, or
stair descending pattern and decides a leg stroke such as a
standing, resting, grounding, or a kicking stroke by comparison
with a basic leg action pattern, calculates a target
bending/stretching position corresponding to the detection signal
from the bending/stretching sensor 51 with reference to basic mode
data, and outputs the calculated result to the actuator 20 as a
target value. At the same time, the electronic control unit 37
calculates heat which corresponds to the target value and is to be
generated by the combustor 14 and outputs a control signal to the
fuel adjuster 44.
[0064] The manually operated controller 40 changes a phase
difference between the displacer piston 13 and the power piston 48,
and gives an instruction to start/stop the whole system to the
electronic control unit 37. In particular, when the prosthetic leg
1 is intended to move up or down to or from a step portion larger
than that of a usual stair, the manually operated controller 40
outputs a signal for instructing an increase/decrease in the
bending/stretching angle.
[0065] A second embodiment of the present invention shown in FIG. 7
will be described below. According to the second embodiment, a
hydraulic converter 53 for converting the pressure in the
compression chamber 12 into a hydraulic pressure is provided on the
displacer unit 6. An output port of the hydraulic converter 53 is
connected to the operation chamber 49 of the power cylinder 47 via
the pressure conduit 22. The other configurations are the same as
those of the first embodiment, and therefore, parts in FIG. 3
corresponding to those in the first embodiment are designated by
the same reference numerals and the overlapped description thereof
is omitted.
[0066] According to the second embodiment, since the pressure in
the compression chamber 12 of the displacer unit 6 is converted
into a hydraulic pressure by the hydraulic converter 53, and the
hydraulic pressure is transferred to the operation chamber 49 of
the power cylinder 47. Thus, it is possible to eliminate the
occurrence of elastic compression, which has been caused for a
working gas, in the pressure conduit 22 and the operation chamber
49, and hence to improve a pressure transmission efficiency.
Further, since the pressure conduit 22 is filled with a
non-compressive fluid, it is possible to eliminate a possibility
that the inner volume of the pressure conduit 22 becomes a dead
volume of the Stirling engine E, and hence to improve a theoretical
efficiency of the Stirling engine E.
[0067] A third embodiment shown in FIG. 8 will be described below.
In the third embodiment, a Stirling engine E is used for
controlling a posture of a seat of a wheelchair W. In the
wheelchair W, a seat 76 is connected via an X-type link mechanism
75 to a frame 74 for supporting a wheel 73. A displacer unit 6 of
the Stirling engine E is mounted to a back surface of the frame 74,
and a power piston 48 and a power cylinder 47 of a power cylinder
unit 8 are connected to the frame 74 and the seat 76, respectively.
An inclination sensor (not shown) is mounted to the seat 76. On the
basis of an output signal from the sensor, an actuator 20 of the
displacer unit 6 is operated in such a manner that an inclination
angle of the seat 76 becomes zero, to drive the power piston 48.
With this posture control of the seat, it is possible to usually
keep the seat 76 in a horizontal state irrespective of the
inclination of a road surface, and hence to improve the seating
comfort, and also it is possible to realize a long-time drive while
suppressing an increase in weight of the wheelchair W by using the
Stirling engine E.
[0068] A fourth embodiment of the present invention shown in FIG. 9
will be described below. A power piston 48 of the Stirling engine E
drives a power generator 81 via a crank mechanism 80. An output
side of the power generator 81 is connected to a load apparatus 83
such as a battery or an electric motor via load adjusting means 82.
The load adjusting means 82, which is adapted to adjust a load
applied to the load apparatus 83, is controlled by the electronic
control unit 37 on the basis of detection signals from a displacer
piston sensor 21 and a power piston sensor 51.
[0069] The other configurations are the same as those of the
Stirling engine according to the first embodiment, and therefore,
parts in FIG. 9 corresponding to those in the Stirling engine E
according to the first embodiment are designated by the same
reference numerals and the overlapped description thereof is
omitted.
[0070] According to the fourth embodiment, even if heat generated
by the combustor 14 of the displacer unit 8 is somewhat varied, the
output from the power piston 48 can be stabilized.
[0071] A fifth embodiment of the present invention shown in FIG. 10
will be described below. A Stirling engine E according to the fifth
embodiment includes a pair of displacer units 6A and 6B and a
single double-acting type power cylinder unit 8. The pair of
displacer units 6A and 6B are disposed in a state in which head
portions of displacer cylinders 10 of the displacer units 6A and 6B
are opposed to each other. A common combustor 14 for heating both
the head portions of the displacer cylinders 10 is provided so as
to surround both the head portions of the displacer cylinders 10.
Rods 13a of displacer pistons 13 of both the displacer units 6A and
6B are integrally connected to each other via a connection link 54
and also connected to a common control actuator 20. In this case, a
phase difference of 90.degree., which is a value converted in a
crank angle, is given between the displacer pistons 13 of the
displacer units 6A and 6B. The other configurations of each of the
displacer units 6A and 6B is the same as those of the displacer
unit 6 in the first embodiment, and therefore, parts shown in FIG.
10 corresponding to those described in the first embodiment are
designated by the same reference numerals and the overlapped
description thereof is omitted.
[0072] The double-acting type power cylinder unit 8 includes a
power cylinder 47 with both ends closed, and the inside of the
power cylinder 47 is partitioned into first and second operation
chambers 49A and 49B by a power piston 48 fitted in the power
cylinder 47. These first and second operation chambers 49A and 49B
are connected to compression chambers 12 of the first and second
displacer units 6A and 6B via flexible first and second pressure
conduits 22A and 22B, respectively. An output rod 48a of the power
piston 48 passes through one end wall of the power cylinder 47, and
drives a load (not shown).
[0073] With this configuration, when the displacer pistons 13 of
the first and second displacer units 6A and 6B are simultaneously
reciprocated by the control actuator 20 via the connection link 54,
pressure amplitudes are alternately generated in the compression
chambers 12 of the displacer units 6A and 6B, so that the first and
second operation chambers 49A and 49B in the power cylinder 47 are
alternately boosted, to drive the power piston 48 in the
reciprocating directions.
[0074] Even in the fifth embodiment, both the first and second
displacer units 6A and 6B and the power cylinder unit 8 can be
disposed separately from each other and also displaced relative to
each other. Further, the motion of the power piston 48 of the power
cylinder unit 8 can be freely remote-controlled by controlling the
phases and operation speeds of both the displacer pistons 13 by the
control actuator 20.
[0075] A sixth embodiment of the present invention shown in FIG. 11
will be described below. The sixth embodiment has the same
configuration as that of the fifth embodiment shown in FIG. 10,
except that first and second displacer units 6A and 6B are disposed
in parallel with their head positions of the displacer cylinders 10
directed in the same direction, and rods 13a of displacer pistons
13 are connected to both ends of an I-type lever 56 swingably
supported by a fixed pivot 55 via links 57 and a common actuator 20
is connected to one end of the lever 56. It is to be noted that
parts corresponding to those in the fifth embodiment are designated
by the same reference numerals and the overlapped description
thereof is omitted.
[0076] A seventh embodiment of the present invention shown in FIGS.
12(a), 12(b) and 12(c) will be described below. First and second
displacer units 6A and 6B are disposed in parallel with head
portions of the displacer cylinders 10 directed in the same
direction. First and second control actuators 20A and 20B, which
are individually operable, are connected to displacer pistons 13 of
the displacer units 6A and 6B, respectively.
[0077] First and second power cylinder units 8A and 8B are disposed
in parallel so as to correspond to the first and second displacer
units 6A and 6B, respectively. Operation chambers 49 of the power
cylinder units 8A and 8B are connected to compression chambers 12
of the first and second displacer units 6A and 6B via first and
second pressure conduits 22A and 22B, respectively.
[0078] Each of the first and second power cylinder units 8A and 8B
is of a single-acting type, and an operational member 59 is
connected to output rods 48a of power pistons 48 of the first and
second power cylinder units 8A and 8B via links 58.
[0079] In FIGS. 12(a), 12(b) and 12(c), parts of the first and
second displacer units 6A and 6B, corresponding to those in the
sixth embodiment shown in FIG. 11, are designated by the same
reference numerals and the overlapped description thereof is
omitted.
[0080] According to the seventh embodiment, as shown in FIGS.
12(a), 12(b) and 12(c), by individually operating the first and
second control actuators 20A and 20B at suitable times, the power
pistons 48 of the first and second power cylinder units 8A and 8B
can be alternately operated with a phase difference of 90.degree.,
which is a value converted in crank angle, given therebetween, the
phases of the power pistons 48 can be changed, and the operational
member 59 can be swung or translated. Accordingly, it is possible
to realize a complicated action of the operational member 59.
[0081] While not shown in FIGS. 10 to 12(c), the Stirling engine E
in each of the fifth to seventh embodiments includes the same
displacer piston sensor 21, power piston sensor 51, and control
unit 37 as those described in the first embodiment.
[0082] The present invention is not limited to the above-described
embodiments, and it is to be understood that various changes in
design may be made without departing from the scope of the present
invention.
[0083] As described above, according to the first feature of the
present invention, there is provided a Stirling engine including a
displacer unit in which a displacer piston is slidably fitted in a
displacer cylinder so as to partition the inside of the cylinder
into an expansion chamber and a compression chamber, and a power
cylinder unit in which a power piston is slidably fitted in a power
cylinder so as to form an operation chamber in communication with
the compression chamber in the cylinder. The displacer unit and the
power cylinder unit are disposed separately from each other. The
compression chamber is connected to the operation chamber via a
pressure conduit. A control actuator, capable of arbitrarily
controlling the displacer piston, is connected to the displacer
piston. With the first feature, the displacer unit and the power
cylinder unit can be disposed separately from each other, more
specifically, freely disposed at desired positions. As a result, it
is possible to increase the degree of freedom in layout of the
Stirling engine and thereby to enhance the applicability of the
Stirling engine. Further, the power piston of the power cylinder
unit can be freely remote-controlled by controlling a phase and an
operating speed of the displacer piston by means of the control
actuator.
[0084] According to the second feature of the present invention, in
addition to the first feature, the pressure conduit has
flexibility. With this second feature, the displacer unit and the
power cylinder unit can be displaced relative to each other by the
flexibility of the pressure conduit, so that the displacer unit and
the power cylinder unit can be disposed without interference
therebetween. As a result, it is possible to further increase the
degree of freedom in layout of the Stirling engine and hence to
further enhance the applicability of the Stirling engine.
[0085] According to the third feature of the present invention, a
hydraulic converter for converting a pressure in the compression
chamber to a hydraulic pressure and transmitting the hydraulic
pressure to the operation chamber is provided between the
compression chamber and the pressure conduit. With this third
feature, since a pressure of the compression chamber of the
displacer unit is converted into a hydraulic pressure by the
hydraulic converter and the hydraulic pressure is transmitted to
the operation chamber, elastic compression, which is liable to
occur in the case of using a working gas as a transmission medium,
does not occur in both the pressure conduit and the operation
chamber. Thus, it is possible to improve a pressure transmission
efficiency. Further, since the pressure conduit is filled with a
non-compressive fluid, it is possible to eliminate a possibility
that an inner volume of the pressure conduit becomes a dead volume
of the Stirling engine, and hence to improve a theoretical
efficiency of the Stirling engine.
[0086] As described above, according to the fourth feature of the
present invention, there is provided a control system for a
Stirling engine including a displacer unit in which a displacer
piston is slidably fitted in a displacer cylinder so as to
partition the inside of the cylinder into an expansion chamber and
a compression chamber. A power cylinder unit is provided in which a
power piston is slidably fitted in a power cylinder so as to form
an operation chamber communicated to the compression chamber in the
cylinder. The control system includes a displacer piston driving
means for driving the displacer piston, a displacer piston position
detecting means for detecting a position of the displacer piston, a
power piston position detecting means for detecting a position of
the power piston and a control unit for controlling an operation of
the displacer driving means on the basis of detection signals from
both piston position detecting means. With this feature it is
possible to control the motion of the power piston with a high
responsiveness by operating the displacer piston at a suitable time
by the displacer driving means, and hence to increase the
applicability of the Stirling engine. In particular, since the
operation of the displacer driving means is controlled by the
control unit on the basis of detection signals from the displacer
piston position detecting means and the power piston position
detecting means, it is possible to freely control the operation,
stoppage, an operating speed, and a stopped position of the power
piston irrespective of heat generated by the heating portion of the
displacer unit.
[0087] According to the fifth feature of the present invention, in
addition to the fourth feature, the displacer piston driving means
is operated by the control unit so as to change a difference in
phase between the displacer piston and the power piston. With this
second feature, it is possible to freely control an operating
timing and a stopping timing of the power piston.
[0088] According to the sixth feature of the present invention,
there is provided a control system for a Stirling engine including
a displacer unit in which a displacer piston is slidably fitted in
a displacer cylinder so as to partition the inside of the cylinder
into an expansion chamber and a compression chamber. A power
cylinder unit is provided in which a power piston is slidably
fitted in a power cylinder so as to form an operation chamber in
communication with the compression chamber in the cylinder. The
control system being includes a displacer piston driving means for
driving the displacer piston, a heat control means for controlling
heat generated by a heating portion of the displacer cylinder, a
displacer piston position detecting means for detecting a position
of the displacer piston, a power piston position detecting means
for detecting a position of the power piston and a control unit for
controlling an operation of the heat control means on the basis of
detection signals from both piston position detecting means.
[0089] With this sixth feature, it is possible to control the
motion of the power piston with a high responsiveness by operating
the displacer piston at a suitable time by the displacer driving
means, and hence to increase the applicability of the Stirling
engine. In particular, since the operation of the heat control
means for controlling heat generated by the heating portion of the
displacer cylinder is controlled by the control unit on the basis
of detection signals from the displacer piston position detecting
means and the power piston position detecting means, it is possible
to efficiently use heat generated by the heating portion.
[0090] According to a seventh feature of the present invention,
there is provided a control system for a Stirling engine including
a displacer unit in which a displacer piston is slidably fitted in
a displacer cylinder so as to partition the inside of the cylinder
into an expansion chamber and a compression chamber. A power
cylinder unit is provided in which a power piston is slidably
fitted in a power cylinder so as to form an operation chamber in
communication with the compression chamber in the cylinder. The
control system includes a displacer piston driving means for
driving the displacer piston, a load adjusting means for adjusting
a load of a load apparatus connected to the power piston, a
displacer piston position detecting means for detecting a position
of the displacer piston, a power piston position detecting means
for detecting a position of the power piston and a control unit for
controlling an operation of the load adjusting means on the basis
of detection signals from both piston position detecting means.
[0091] With this fourth feature, it is possible to control the
motion of the power piston with a high responsiveness by operating
the displacer piston at a suitable time by the displacer driving
means, and hence to increase the applicability of the Stirling
engine. In particular, since the operation of the load adjusting
means is controlled by the control unit on the basis of detection
signals from the displacer piston position detecting means and the
power piston position detecting means, it is possible to stabilize
the output from the power piston even if the heat generated by the
heating portion is somewhat varied.
[0092] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *